1. Field of Invention
This invention relates to optical fiber connectors and, more particularly, to fiber-optic connectors having identical connector halves in which manufacturing tolerance errors are reduced and the fibers to be coupled are mated with each other so as to minimize transmitted light losses. The connector is easily field-installed and replaced.
2. Description of the Prior Art
Fiber-optic transmission lines sometimes known as optical fiber waveguides are capable of high frequency transmissions over a long distance with relatively small losses. The fiber optic transmission line consists of a core of dielectric transparent material surrounded by a layer of transparent cladding material having a refractive index which is lower than that of the core. To make such fibers practical for optical communication systems, a low loss connector for quickly and conveniently connecting sections of fiber together is needed. Such a connector must cause light to be coupled from one fiber to another with little loss of signal, i.e., with low insertion loss.
For reasonably low insertion losses to be achieved, the centers of the fiber end faces must, therefore, be registered. Furthermore, due to the high numerical aperture of many optical waveguides, fiber alignment is especially important. Since light diverges from the fiber axis as it travels through a fiber interface, some light is lost if the end faces of the fibers are separated; therefore, the end faces of the fibers should be maintained in virtual contact. Fiber-to-fiber separation also implies an insertion loss due to Fresnel reflections at one of the two glass end interfaces.
U.S. Pat. No. 4,088,386 discloses an optical fiber connector comprising a first resilient member having an elongated V-shaped groove in the surface thereof into which two fibers to be optically connected are disposed end-to-end. A second resilient member is urged against that portion of the fibers opposite the first member, thereby causing a slight deformation of the second member and the slot forming walls. The substantial equilibrium of forces applied to the two fibers by the resilient members causes their axes to reduce misalignment. This arrangement and the other known arrangements for connecting optical fibers suffer from one or more of the following disadvantages: The connectors are expensive, generally due to the necessity of having precision parts which require considerable time and labor to manufacture. Many of the known arrangements require the use of slow drying epoxies which require long curing times. Many of the arrangements require grinding and polishing of the ends of the optical fibers, which actions are not easily performed in the field. Many of the arrangements are not sufficiently self-centering to overcome the losses due to manufacturing tolerance buildup in the coupling mechanism. For example, the use of rubber or plastic members in the connector introduce errors due to shrinkage after molding or casting. The fibers are often concealed so that they are not easily inspected and cleaned as required in maintenance and trouble shooting.